The proposed study is a Type 2 Effectiveness-Implementation Hybrid Trial. Aim 1 will experimentally test the effectiveness of a motivational interviewing-based brief intervention (BI) for substance use within community- based HIV/AIDS service organizations, relative to usual care (UC). Aim 2 will test the effectiveness of adding an organizational-level implementation intervention called Implementation & Sustainment Facilitation (ISF) to the implementation strategy currently used by SAMHSA-funded Addiction Technology Treatment Centers (ATTCs; i.e., staff workshop training + feedback + coaching). Aim 3 will examine the incremental cost- effectiveness of the ISF implementation intervention. Over the course of the five-year project, 42 community- based HIV/AIDS service organizations will be randomized to one of two implementation conditions (ATTC-only vs. ATTC+ISF). Across conditions, two frontline HIV/AIDS service organization staff from each participating HIV/AIDS organization will be selected at random and invited to receive the usual ATTC staff-focused BI training model. In addition, HIV/AIDS organizations assigned to the ATTC+ISF condition will receive the ISF intervention, which focuses on providing feedback and coaching to organizational leadership. During the Initial Implementation stage of the study, approximately 72 clients from each of the 42 organizations (3,024 clients in total) will be randomized to one of two clinical conditions (UC vs. UC+BI). Clients in both conditions will receive the organization's respective UC for substance use (i.e., referral to treatment). In addition, clients assigned to UC+BI will receive a 20-30 minute motivational interviewing-based BI as delivered by one of two BI trained staff. Aim 1 will examine 3-month improvements in client-level measures of Alcohol and Other Drug (AOD) Change Readiness, Days of AOD Treatment, and Antiretroviral Therapy (ART) adherence. Aim 2 will examine client-level implementation outcome measures including independently rated assessments of BI adherence and competence (i.e., BI Integrity) conducted by trained raters blind to condition assignment. Finally, Aim 3 will include estimating costs of th implementation strategies, which will be measured from the perspective of program providers in order to increase the real-world usefulness of the results, with the relative cost-effectiveness of the two implementation conditions being assessed using both incremental cost- effectiveness ratios (ICERs) and cost-effectiveness acceptability curves (CEACs). Although substance use among people living with HIV/AIDS has been associated with increased psychiatric problems, poorer HIV viral suppression, poorer HIV medication adherence, and increased likelihood of engaging in risk behaviors that result in infection transmission to others, integration of substance use and HIV/AIDS services remains limited. The proposed study seeks to address this gap by providing new knowledge regarding the effectiveness of BI for substance use within community-based HIV/AIDS service settings, as well as new knowledge regarding how to address the well-documented underutilization of evidence-based practices in real-world settings.